Implantable medical devices (IMDs) such as pacemakers and implantable cardioverters/defibrillators (ICDs) typically have a non-rechargeable battery with an expected lifetime of 3-15 years, with 5-10 years being most common. This has been made possible with advancements in battery and capacitor technology, as well as reducing power requirements of the components within the device. At the same time, many more features, therapies and capabilities are provided in modern IMDs that simply require additional power.
Pacemakers generally require at least two electrodes to deliver electrical therapy to the heart and to sense the intracardiac electrogram. Traditionally, pacemaker systems are comprised of an implantable pulse generator and lead system. The pulse generators are implanted under the skin and connected to a lead system that is implanted inside the heart with at least one electrode touching the endocardium. The lead system can also be implanted on the epicardial surface of the heart.
Leadless pacemakers (LPMs) may also be used to deliver cardiac stimulation. In the case of intercommunication between a LPM that is configured to fit within a chamber of a patient's heart and a programmer, however, the power source of the LPM is heavily constrained due to patient anatomy and related safety issues. Any excess power consumption needed for implant to programmer (“i2p”) communication will reduce device battery/power cell longevity of the implant, requiring the patient to undergo more frequent operations to have their implants replaced.
An implantable cardiac monitor (ICM) enables physicians to evaluate heart rhythm signals over a longer period of time than allowed by conventional monitoring, and is designed to help diagnose and document difficult-to-detect rhythm disorders in patients who may suffer from unexplained symptoms, including syncope (the sudden and transient loss of consciousness), palpitations and shortness of breath. An ICM may be implanted subcutaneously in the upper chest region and is approximately the size of a computer thumb drive, enabling delivery using an outpatient procedure, under local anesthesia, with little patient discomfort. The ICM communicates with a programmer, allowing real-time data to be remotely sent to a health care provider. However, because of the small size of the ICM, the size of the power source of the ICM is also heavily constrained.
Power management is a very important aspect in the design and manufacture of IMDs and, in particular, power management for efficient and reliable communication between a programmer and smaller IMDs, such as LPMs, ICMs, and other hemodynamic monitors, where power resources are especially scares.
In addition, IMD orientations and geometries may affect signal strength and therefore reliability of communication between the IMD and a programmer.